These days, hybrid cars become widespread, so that high voltage resistance and high heat resistance are required of wires and connectors for automobile. Conventionally, crosslinked polyvinyl chloride (PVC) wires or crosslinked polyolefin wires are used at sites where high heat is generated such as wiring harnesses in automobiles. These wires are mostly crosslinked by electron irradiation; however, there arises a problem that the electron irradiation crosslinking requires expensive crosslinking devices and facilities to cause an increase in production cost. Thus, water-crosslinking receives attention, in which a crosslinkable resin (water-crosslinkable resin) that is obtained by modifying a polyolefin resin by a silane coupling agent is used, because the crosslinking can be performed by inexpensive facilities (see PTLs 1 and 2, for example).
For example, PTL 1 discloses a non-halogenous flame-retardant silane-crosslinked polyolefin composition that is prepared by heat-kneading, and crosslinking a silane graftmer (A component) and a catalyst master batch (B component), where the silane graftmer (A component) is prepared by kneading a compound and 100 parts by mass of magnesium hydroxide, the compound being prepared by graft-polymerizing a silane coupling agent onto a polyolefin elastomer by heat-kneading 100 parts by mass of polyolefin elastomer, 1 to 3 parts by mass of silane coupling agent and 0.025 to 0.063 parts by mass of cross-linking agent, and where the catalyst master batch (B component) is prepared by impregnating 100 parts by mass of polyolefin elastomer with 1.0 to 3.12 parts by mass of cross-linking agent and 7.14 to 31.3 parts by mass of a cross-linking catalyst.
In addition, PTL 2 discloses, as a composition for a wire coating member, a resin composition for use by mixing with silane-crosslinkable polyolefin, the resin composition containing 100 parts by mass of at least one polymer that is selected from a group consisting of a thermoplastic resin, rubber and a thermoplastic elastomer 0.01 to 0.6 parts by mass of organic peroxide, 0.05 to 0.5 parts by mass of silanol condensation catalyst, and 100 to 300 parts by mass of magnesium hydroxide.